The invention relates to computer systems and, more particularly, to a method for host protection during hot swap in a pipelined network.
In a pipelined network, such as a Peripheral Component Interconnect (PCI) network, a bridge can be used in order to provide a means of conveying information across multiple constituent bus segments. The use of multiple bus segments enables the network to include more peripheral components than would be possible if only a single bus segment were to be used. Additionally, the use of a bridge in a pipelined network provides a means of increasing the aggregate bandwidth of the network by allowing transactions to initiate and terminate within a bus segment without involving the entire network.
In a high-availability system which incorporates a bridged multi-segmented network, transactions which are initiated at a peripheral component which is interfaced to a secondary bus segment can remain in the network since each bridge typically incorporates a capability to store a transaction as the transaction is bridged between bus segments. This capability allows the bridge to forward the transaction through the network hierarchy and place the transaction on a target bus as the intervening buses become available and able to accept the new transaction. Among these are transactions which allow the direct memory access of areas within the host computer memory space by particular peripheral components.
In a bridged, pipelined network operating in a high-availability environment, a hot swap of a host computer while a direct memory access transaction exists at a bridge located within the bus hierarchy can degrade the new host computer. This event can be made possible if the new host computer includes a memory allocation scheme which is not identical to the memory allocation scheme of the previous host computer. Therefore, during the moments immediately after the hot swap of the host computer, direct memory access transactions intended for the previous host computer can degrade and, in some cases, temporarily suspend (i.e. crash) operations on the network.
Therefore, what is needed, is a method for host protection during hot swap in a bridged, pipelined network. This type of method can be useful in 5 preserving the integrity of the new host computer after the removal and replacement of the previous host computer.